<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<script type="text/javascript">
			var str1 = "Hello jS!";
			console.log(str1.toLowerCase());//hello js!
			console.log(str1.toUpperCase());//HELLO JS！
			console.log(str1.charAt(6));//j
		</script>
	</head>
	<body>
	</body>
</html>
